Demands have been recently made on electronic components to have reduced sizes and increased precise. Ceramic capacitors, for example, must have reduced sizes such as “0603” size and “0402” size and have larger capacities as a result of high integration of layers in a number exceeding several hundreds. In particular, satisfactory processing accuracy has been required to realize size reduction and precision increase in laminating of ceramic sheets before firing (ceramic green sheets) typically for constituting ceramic capacitors.
Taking a method for producing a ceramic capacitor as an example, it includes, for example, the steps (processes) of (1) printing electrodes to green sheets, (2) laminating the printed green sheets, (3) pressing (pressing under pressure), (4) cutting, and (5) firing, in which the cutting process (4) is conducted after repeating the laminating process (2) and the pressing process (3) predetermined times.
Required precisions (accuracies) on these processes include the precision of printing electrodes in the process (1) of printing electrodes to green sheets; the precision of aligning electrodes in the laminating process (2); the precision of preventing misregistration of electrodes due to deformation of the green sheets as a result of pressurization in the pressing process (3); and the precision of cutting in the cutting process (4). Products become defective and have decreased productivity even when only one of these precisions is low in these processes.
Of these, the precisions required in the process (1) of printing electrodes to green sheets, the laminating process (2), and the cutting process (4) are mechanical precisions, and they can be achieved by realizing improvements in apparatuses and in precision. In the pressing process (3), however, the green sheets may deform and undergo misregistration as a result of pressurization (pressing under pressure), and this may cause the misregistration of electrodes and affect the precision of electrode registration in the green sheets laminated in the laminating process (2).
In current laminating processes (2), green sheets are generally laminated on poly(ethylene terephthalate) films (PET films) or pressure-sensitive adhesive tapes. Among them, the lamination of green sheets on pressure-sensitive adhesive tapes is increasingly employed from the viewpoints of size reduction and satisfactory anchoring (fixing) of green sheets in the subsequent cutting process.
Pressure-sensitive adhesive tapes used herein are adhesive tapes that exhibit tackiness (pressure-sensitive adhesion) at ordinary temperature so as to adhere to (fix) green sheets during the laminating process, pressing process, and cutting process, and have decreased tackiness as a result typically of heating or irradiation with ultraviolet rays, and can be peeled off after the cutting process. Examples of such adhesive tapes are heat-peelable pressure-sensitive adhesive sheets each including a substrate and a heat-expandable pressure-sensitive adhesive layer arranged at least on one side of the substrate; ultraviolet curable/peelable pressure-sensitive adhesive sheets; and low-tack adhesive tapes, as disclosed typically in Japanese Examined Patent Application Publication (JP-B) No. Sho 50-13878, JP-B No. Sho 51-24534, Japanese Unexamined Patent Application Publication (JP-A) No. Sho 56-61468, JP-A No. Sho 56-61469, and JP-A No. Sho 60-252681. More specifically, taking heat-peelable pressure-sensitive adhesive sheets as an example, they show both adhesiveness before heating and peelability after heating. Namely, after achieving the target adhesion, heat-expandable microspheres in the heat-expandable pressure-sensitive adhesive layer are heated to foam or expand, and the surface of the heat-expandable pressure-sensitive adhesive layer becomes uneven. This reduces the adhesion area (contact area) with an adherend (work) to thereby reduce the adhesive strength. Thus, the adherend can be easily peeled off (separated) from the adhesive tapes.